It is known that many materials, such as carbon/carbon composites, carbon fibers, graphite, and certain metals, have properties which make them attractive for use in aerospace and other applications in which their susceptibility to oxidative deterioration at elevated temperatures is a serious disadvantage. It would be desirable to find a means of protecting those materials from oxidation at high temperatures, and it has been proposed to provide such protection with ceramic coatings. However, known ceramic coatings have proved to be inadequate.
As disclosed in U.S. Pat. Nos. 4,397,828 (Seyferth et al.-I) 4,482,669 (Seyferth et al.-II), 4,645,807 (Seyferth et al.-III) 4,650,837 (Seyferth et al.-IV) and 4,659,850 (Arai et al.), it is known that ceramics can be obtained from polysilazanes. U.S. Pat. No. 4,482,689 (Haluska) discloses boron-containing metallosilazane polymers which are also useful in forming ceramic materials.